$PbTiO_3$ thin films were deposited onto silicon substrate by atmospheric pressure(AP) and reduced pressure(RP) chemical vapor depositions.
In the APCVD, we have used Pb powder and ethyl titanate[$Ti(C_2H_5O)_4$] as the source material of Pb and Ti vapor and various substrates such as Si, Ti/Si, and $TiO_2/Si$. $PbTiO_3$ thin films were deposited on the Si and Ti/Si substrates and lead silicates were formed on the Si and Ti/Si substrates as second phase. The results of AES analysis revealed the $TiO_2$ layer on the Si substrate conducted as diffusion barriers between Si substrate and $PbTiO_3$ films. Lead oxide solid solution were observed as second phase in the films deposited on $TiO_2$/Si substrate, and were removed by annealing at 800 ℃ for 2 hr. The effects of Ti$(C_3H_7O)_4$ input fractions and oxgen partial pressures on the $PbTiO_3$ thin film deposition were investigated. Due to the gas phase decomposition of Ti$(C_2H_5O)_4$, these reaction parameters affected the amount of adsorbed $TiO_2$ on the substrate surface and the phase of deposited films.
The growth mechanism of $TiO_2$ and PbO thin films from Ti$(C_3H_7O)_4$ and Pb $(dpm)_2$ were investigated in the RPCVD system.
The $TI(C_3H_7O)_4$ input fraction and temperature depence of growth rate of $TiO_2$ films showed abnormal behaviors, which could not be explained by homogeneous reaction model neither hetregeneous reaction model. The microstructure and XRD intensity of $TiO_2$ films dramatically depended on the reaction temperature and pressure. Using the modified homogeneous reaction theory, the experimental results were explained. $TiO_2$ thin film growth were controlled by hetrogeneous reaction at low temperatures, homogeneous reaction at high temperatures, and quasi-homogeneous reaction at intermediate temperatures(400-700℃). $TiO_2$ films deposited at intermediate temperature ranges had microcrystalline grains and showed weak XRD intensity.
Due to reactions between PbO and silicon substrate, it was impossible to deposit the single phase PbO thin films onto silicon substrate in this experimental temperature ranges.
The effects of deposition temperature and reactor pressure on $PbTiO_3$ thin film formation were investigated. The $PbTiO_3$ formation temperatures were decreased with increasing reactor pressure due to the reactivity change of adsorbed $TiO_2$ particles. Due to the gas phase reaction of Ti$(C_3H_7O)_4$, the composition variation of deposited films with the deposition temperature were observed. To investigate the interface region between Si and $PbTiO_3$ films AES depth profile were conducted.
The results of high temperature XRD experiments showed the phase transition occurred at 520℃ during heating and at 500℃ during cooling.
